Each image is composed of approximately 20 nearly identical images stacked on top of each other. Capturing one sequence takes about one second. The “ghosts” you see are likely caused by people moving during this time, as is the case with moving cars. Occasionally, you might notice a person’s foot without the rest of their body. This happens because the foot was the only part that remained stationary during the exposure, while the rest of the body was removed by the algorithm used for stacking the images.